Hurricanes are fueled by warm waters and tropical storms, which interact to create regions of warm air that powers the whirling storm. Right now, Igor is a perfect example of heated ocean interacting with freezing thunderheads.

When NASA's Aqua satellite passed over Igor on Sept. 14 at 14:47 UTC (10:47 a.m. EDT) the Atmospheric Infrared Sounder (AIRS) instrument captured icy cold cloud top temperatures in the strong thunderstorms that surround Igor's well-defined eye. Those cloud top temperatures were as cold or colder than -90F, indicating they were near the top of the troposphere, and very strong.

The infrared imagery also showed the warmer, open 20 nautical-mile wide eye (because it was not cloud-filled). In addition, AIRS got a reading on the sea surface temperatures around Igor, which were all warmer than the 80F threshold needed to maintain a tropical cyclone, so Igor has a good energy source for the next day or two. So, the difference between Igor's cold cloud top temperatures and the warm ocean surface waters that are powering it are greater than 170 degrees Fahrenheit!